Generally, a smart grid is seen as a next-generation power network which applies information technology (IT) to the existing power system so that a smart grid observes and controls a power network in real time and optimizes the operation efficiency of the power network through the bidirectional communication between power providers and consumers. In addition, a smart grid can be used in association with new electric equipments that are recently in great demand, such as a renewable energy generation system or a charge system for electric vehicles, and can improve power utilization efficiency by providing consumers' power usage information in real time, thereby decreasing unnecessary investment in power facilities and emission of greenhouse gases. Recently, smart grids have gained much attention due to issues of the modernization of a power network and the expansion of a renewable energy which have led to the extensive research of a smart grid.
One of the key technologies in relation to a smart grid is a power storage system. A power storage system provides load leveling by storing electric power during off-peak periods and using the stored power during on-peak periods, thereby contributing to the efficient use of power equipments. Conventionally, a pumped-storage power generation, which converts nocturnal surplus power into kinetic energy of water and saves the kinetic energy, and a chemical energy storage method, which combines multiple lead-acid battery cells to each other in series or in parallel, were commonly used.
However, a pumped-storage power generation absorbs enormous construction costs, since it requires large quantities of water and particular geographical conditions. In the case of a lead-acid battery cell, due to low energy storage density, a high-voltage and large-capacity power storage system cannot be established. Meanwhile, with the development of a lithium-ion battery having high energy density, a high-voltage and large-capacity power storage system by using a chemical energy storage method is now possible.
A power storage system using a chemical energy storage method includes battery modules configured with lithium ion batteries having high energy density, and a predetermined number of the battery modules are electrically connected to each other and loaded in a rack system with a multi-stage form.
In order to load battery modules, a rack system should maintain certain temperature and humidity; be ventilated well; and facilitate easy maintenance and repair.
A conventional rack system of a power storage system where battery modules are loaded will be explained below with reference to the accompanying drawings.
FIG. 1 is a schematic perspective view showing a conventional rack system of battery modules.
As shown in FIG. 1, the conventional rack system 10 includes a rack assembly 13 having frames 11 and panels 12, and a plurality of shelves 14 on which a predetermined number of battery modules 1 are installed in a multi-stage form. The plurality of shelves 14 are fixed to the frames 11 of the rack assembly 13 to have a multi-stage form.
In the conventional rack system 10, since the bottom of each battery module 1 directly contacts the shelf 14, the bottom of the battery modules 1 cannot ventilate. Also, in the conventional rack system 10, the battery module 1 is positioned to match a coupling hole 15 formed in the shelf 14 and the battery module 1 is fixed with the shelf 14 by using a coupling member 16 such as a bolt. However, such a structure requires space expansion, and the assembly of such a conventional rack system 10 is inconvenient.